EUROCONTROL Data Snapshot #47 on ATFM slot tolerance windows

With traffic close to 2019 levels, the EUROCONTROL Network Manager’s ‘All Together Now 2024’ campaign highlights areas which help to optimise network efficiency and keep delays down. The need to respect Air Traffic Flow Management (ATFM) slot tolerance windows is one piece of the puzzle but why is it important and how are we doing so far?

In Europe, demand and capacity imbalances en-route or at airports are primarily addressed through flow management; affected aircraft are assigned new take-off times centrally by the Network Manager in Brussels to prevent overloads at critical locations.

At departure airports, local air traffic control (ATC) and airlines then have to work together to ensure that the aircraft takes off no more than 5 minutes before or 10 minutes after the newly assigned take-off time. A high level of slot adherence – not taking off too early or too late – is essential to maintain safe and efficient air traffic flows and to balance demand with capacity. This provides better predictability and improves resource management at local and network level. Regulation (EU) No 255/2010 requires all states participating in the Single European Sky (SES) Performance Scheme to monitor ATFM slot adherence at airports, aiming for an ATFM slot compliance rate of 80% or higher.

The chart’s yearly view of the summer period (June-August) on the left shows that, despite the share of regulated traffic increasing over the years (brown bar), the percentage of regulated flights departing outside their window (red line) has decreased from 21.3% to 5.6% over the past 20 years - a significant improvement.

An analysis of the top 30 airports in terms of traffic in summer 2024 (listed from left to right) reveals a significant variation in the percentage of regulated flights departing outside their allocated ATFM slot tolerance window. This percentage ranges from 21% at Istanbul-Sabiha Gökçen airport to 0.3% at Oslo airport.

In the past, airport Collaborative Decision Making (A-CDM) implementation and local awareness campaigns have resulted in substantial improvements at airports with poor adherence levels, benefiting the entire European network.

Download the data snapshot here: EUROCONTROL Data Snapshot #47

Download the data snapshot Dataset here: EUROCONTROL Data Snapshot #47 - Dataset